Radio apparatus



July I; 1931. J. N. NoRDLuND RADIO APPARATUS l Filed m4, 1925 oooooo..

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Patented July 7, 1931 donn N. NonnnuNn, orv DETRoI'r, MICHIGAN RADIO, APPARATUS Application. filed May 4,

Y TheV primary 'object' "of myinventionv is to 'pro'vid'ea'n improved; antenna tuning means for'increasingi theselectlvity invradio reception! wherein the inductances an'd capaclties j are 'so connected, arranged and varied that interferingsignals andiother disturbances are sliunted around the'coupling elements, thereby eliminating the same fromjthe` receiving apparatus. j v j Another (')loj'ectv ofv my, improved' devicev provides what may be called' a re-tuning apparatuswhi`ch,mayflbe adjusted so as to` be in resonance with the undesired signals for'providing. anaturali and'leasy pathfor them to pass to vthe ground insteadof through.' the re'- ceiving. apparatus, the parts being so correlatedthatadjustment ofthe auxiliary tuning means will not throw yout or interfere with the adjustment of the main tuning unit. 2c A further object; ofmy invention isto proj vide myi'mproved' devicefwith means oflo'w inductance whereby low'frequency currents or hums such as come from powerlines, troly ley.y wires, etc., are ley-passed and at the same time radio frequency currents are not permitted to pass through said low inductance.

. It is a further objectof my improved de-r vice to provide interference j eliminating ple and inexpensive to manufacture and install, easy to adjust, positive in action and efficient in service.

With the above and .other objects in view, my invention consists in the arrangement, combination and construction of the various parts of my improved device as described in the specification, claimed in my, claims andl 12. A lixed inductance 14 and the capacity 15, either variable or ixed, are connected in series with the inductance 12 and with each other by the conductors 13 and 16. The

n 5 means in a radio apparatus which will be sim- Y 1925'.` Serin No. 27,992".

ground wire 17 connects the capacity 15`with v the ground. n .y 7 j The-by-passunits consisting of the inductance 18 and the capacity 19, the inductance 20 andfthe vcapacity 21 and the'low induotance 22`are separately connected, by meansof the conductors 24, at pointl 23 to the conductor '13, and'at-point 25 tothe ground Wire 17by f means of the conductors-26. These units are V placed in parallel relation'with each other and withl the induc'tance 14 and'thecapacity 15. Y j

Af conventional type receiving set is connectedf with the inductance 14 by means of either `ay conductive or inductive coupling 27; In the practicaloperation of my improved device, the main unit consisting ofthe in- Iductance 12, the conductor 13, the inductance 114, the conductor 16 andthe capacity 15 are tunedto' resonance withthe frequency ofthe desiredsigna-l by the'aid of variable tuning elements so that the vinductance 14 andthe capacity 15 are` individually tuned."V Thus, these elements are in resonance 'with the frequency corresponding withthe wave length desired. vIn other words, if the vinductance 14 and the capacity 15 were removed, the ground Wire 17 broughtup to the lower side of inductance 12,'-there would still be a tuned circuitl consisting of the vantennadl, the inductance 12y and the ground'connection 172 If these elements are in tune or in resonance individually, they mayas a matter of course bein*resonancecollectively. This being the case', the resistancethrough inductance, v14 and-capacity 15 is 10W becausethe impedance of inductance` 14'A and capacity 15 tends to neutralize each other. f

This, may be illustrate'd by reference to Fig. 2-which may be likened to applicants invention, differing only in fact that the antenna ground capacity is represented by the condenserA-f, B being a device to emit a high'frequency current and having al negligibleimpedance through itl Now supposing that the capacity 15 and the inductance 14 are brought to resonance with some particular highA frequency current emitted byl B, and, likewise, the capacity'Ac and `inductance 12 is brought to resonance with the same frel quency, then a condition arises where the inductances 14', l2 and capacities A, l5 are in tune to that particular frequency collectively, or as a whole, and where also the capacity 15 and inductance 14 are in tune individually. Therefore, this series tuned circuit can be regarded as having two individually tuned sections, a condition which applicants invention employs.

Thus, the by-pass units 18-19 and 20-21 connected in parallel with the individually tuned section and providing the said units are not tuned to the wavelength of desired signals, will have much greater impedance to the current of desired signals than the part 14E-15 in antenna unit across which said units are connected, and this being the case, the desired signals will follow the path of low resistance into the receiving set. On. the other hand, each of these by-pass units, if tuned to the frequency of some interfering signal, will readily by-pass the same on account of its resistance to the interfering signals being much less than through the coupling element in a receiving apparatus. Therefore, these interfering signals will not be recorded in the receiving apparatus.

By inserting the low inductance coil 22, low frequency currents that are caused by power lines, etc., are readily by-passed from the receiving unit and at the same time the radio currents are not disturbed.

I desire it to be understood that my improved by-pass units can be used with a variable inductance or capacity, or both con'- nected in series or in parallel with a fixed inductance and a capacity in series, the entire device being placed between the antenna and ground connections of a radio circuit.

It is obvious that various changes may be made in the arrangement, combination and construction of the various parts of my improved device without departing from the spirit of my invention and it is my intention to cover by my claims such changes as may be reasonably included within the scope' thereof.

That I claim is:

l. In combination, a tuning unit consistingl of a variable inductance connected in series with a fixed inductance and a variable capacity interposed between the antenna and ground connections of a radio circuit, low resistance by-pass units for eliminating interfering frequencies, each of said by-pass units comprising an inductance and a variable capacity in series connected in parallel relation with said liXed inductance and variable capacity and a lon7 inductance also connected in parallel relation with said fixed inductance and variable capacity .for by-passing low frequency currents.

2. In combination, a variable inductance having an antenna connection, an individually tuned section, a conductor connecting in series said section to said variable inductance, said section comprising a fixed inductance and a capacity in series, a ground connection leading from said capacity, low resistance bypass units for eliminating interfering frequencies placed in parallel relation with said section, said units comprising an inductance and a capacity one or the other of which is variable, and Wires connecting separately at one point each of said by-pass units with said conductor and said ground connection.

3. In combination, a radio tuning unit comprising a variable tuning means connected in series with an individually tuned section having a fixed inductance and a. capacity in series, said unit interposed between the antenna. and ground connection of a radio circuit and a plurality of individually timed unimpeded by-pass units for eliminating interfering frequencies connected in parallel relation with said section, one or more of said by-pass units comprising a fixed inductance and a variable capacity in series and one of said by-pass units consisting of a low inductance coil for low frequencies.

4. In a radio receiving circuit consisting of f a main tuning unit having an inductance and an individually tuned section, the combination therewith of selectively tunable low resistance tuning units and a low inductance tion for providing paths for undesired signais, low frequencies and other disturbances to pass around said tuned section to the ground, thereby allowing a clear passage connected in parallel relation with said secico through said section for only the desired signals, said selectively tunable units comprising an inductance and a capacity connected in series.

JOHN N. NORDLUND; 

